3 Types of SMT Soldering Processes — Reflow Oven, Wave Soldering Oven, and TH Reflow Soldering

I. Reflow oven

1. Introduction to Reflow Oven

Reflow soldering technology is well-known in the electronics manufacturing industry. The components on various PCBs used in our computers are all soldered to the circuit boards using this process. The equipment contains a heating circuit that heats air or nitrogen to a sufficiently high temperature and blows it onto the circuit board with components already mounted, causing the solder on both sides of the components to melt and bond with the main board. The advantages of this process include easy temperature control, prevention of oxidation during soldering, and more manageable manufacturing costs.

2. Main steps in reflow soldering machine

• Prototyping and preparation: Lay out and position components on the PCB.
• Apply solder paste: Apply solder paste to the soldering areas on the PCB. Solder paste is a viscous material composed of solder and flux.
• Component placement: Use an automatic SMT machine to precisely arrange electronic components on the solder paste on the PCB.
• Transfer to the reflow oven: Transfer the PCB to the reflow oven and heat it by controlling the temperature curve.
• Reflow soldering: In the reflow oven, apply a predetermined temperature curve to the PCB to melt the solder into a liquid state and connect it to the PCB and components.
• Cooling and inspection: After soldering is complete, the PCB must be cooled and undergo visual and functional inspections.

3. Advantages of reflow soldering

• High production efficiency: Compared to other soldering methods, reflow soldering machine can complete the soldering process in a shorter time.
• Component protection: Since the reflow oven uses alternating current heat conduction, the heating of components is very uniform, helping to reduce the risk of overheating or damage to components.
• Wide applicability: Reflow oven is suitable for various components and board layers, from simple two-layer boards to complex multi-layer boards.
• Good repeatability: The process parameters of reflow soldering can be precisely controlled by regulating the temperature curve and time, thereby achieving highly repeatable soldering.

II. Wave Soldering machine

1. Introduction

Wave soldering machine involves directly exposing the soldering surface of a through-hole board to high-temperature liquid solder to achieve soldering. The high-temperature liquid solder maintains an inclined surface, and a special device causes the liquid solder to form wave-like patterns, hence the name “wave soldering.” The primary material used is solder bar.

2. Main Steps of Wave Soldering

• Prototyping and Preparation: Lay out and position components on the PCB.
• Apply Solder Paste: Apply solder paste to the soldering areas on the PCB.
• Component Placement: Use a pick and place machine to precisely arrange electronic components onto the solder paste on the PCB.
• Transfer to Wave Soldering Machine: Transfer the PCB to the wave soldering machine.
• Solder Dripping: Pre-melted solder is blown upward through the wave soldering machine to form a wave, allowing the PCB pads to come into contact with the solder wave.
• Cooling and Inspection: After soldering is complete, the PCB must be cooled and undergo visual and functional inspections.

3. Advantages of Wave Soldering

• Suitable for Mass Production: Wave soldering is suitable for large-scale SMT production, enabling the simultaneous soldering of multiple joints.
• Suitable for single-sided PCBs: Wave soldering is suitable for single-sided PCBs or double-sided PCBs with low component density.
• Lower cost: Compared to other soldering methods, wave soldering has relatively lower equipment and operational costs.
• High soldering reliability: Since the solder wave directly contacts the pads, wave soldering typically provides reliable solder joints.

III. Through-Hole Reflow Soldering

1. Introduction

THR (through-hole reflow soldering) is a soldering process in through-hole mounting technology and belongs to a type of reflow soldering technology. This process involves inserting component leads into PCB through-holes, then heating and solidifying solder paste to achieve electrical connections. Solder paste, a key material composed of tin powder and flux, is used in the surface mount soldering process.

2. Main Steps of Through-Hole Reflow Soldering

• Prototyping and preparation: Lay out and position components on the PCB.
• Apply solder paste: Apply solder paste to the soldering areas on the PCB.
• Place components: Use an automatic pick-and-place machine to precisely arrange electronic components on the solder paste on the PCB.
• Transfer to the through-hole reflow soldering machine: Transfer the PCB to the through-hole reflow soldering machine.
• Reflow soldering: In the through-hole reflow soldering machine, the solder is melted into a liquid state according to a specified temperature curve and bonded to the PCB and components.
• Solder wave: After soldering is complete, the wave soldering module of the through-hole reflow soldering machine draws the solder up in a wave-like pattern, forming another wave soldering process to reinforce the solder joints.
• Cooling and inspection: After welding is complete, the PCB must be cooled and undergo visual and functional inspections.

3. Advantages of through-hole reflow soldering

• Combines the advantages of reflow soldering and wave soldering: Through-hole reflow soldering combines the high efficiency of reflow soldering with the reliable soldering of wave soldering.
• Suitable for complex PCBs: Through-hole reflow soldering is suitable for complex multi-layer PCBs, providing high-quality connections.
• High production efficiency: Compared to traditional wave soldering, through-hole reflow soldering can save more production time.

Conclusion

Reflow soldering, wave soldering, and through-hole reflow soldering are three commonly used SMT soldering processes. Reflow soldering is suitable for various components and board layers, offering high production efficiency and good repeatability. Wave soldering is suitable for mass production and single-sided boards, with lower costs. Through-hole reflow soldering combines the advantages of reflow soldering and wave soldering, making it suitable for complex PCBs and applications requiring stronger connections. Selecting the appropriate SMT soldering process is crucial for ensuring soldering quality and improving production efficiency.

Company profile

Zhejiang NeoDen Technology Co., LTD., founded in 2010, is a professional manufacturer specialized in SMT pick and place machine, reflow oven, stencil printing machine, SMT production line and other SMT Products. We have our own R & D team and own factory, taking advantage of our own rich experienced R&D, well trained production, won great reputation from the world wide customers.

In this decade, we independently developed NeoDen4, NeoDen IN6, NeoDen K1830, NeoDen FP2636 and other SMT products, which sold well all over the world. So far, we have sold more than 10,000pcs machines and exported them to over 130 countries around the world, establishing a good reputation in the market. In our global Ecosystem, we collaborate with our best partner to deliver a more closing sales service, high professional and efficient technical support.